1. Field of the Invention
The present invention relates to valve stem seals, and more particularly to a valve stem seal for use on a valve guide.
2. Description of Related Art
Numerous valve stem seals have been developed for internal combustion engines. Numerous attempts have also been made to create a low friction seal which resists wear in high temperature environments. Various materials have been tried such as ceramics, metal, copper, bronze, and/or brass alloys. An example of a prior art valve guidance seal member can be found in U.S. Pat. No. 4,798,181.
It is desirable in an internal combustion engine to maintain a uniform film of lubricating oil between the valve stem and the valve guide to reduce wear, extend durability and promote a reduced friction environment thus conserving or saving energy and reducing heat of operation. When the valve guide becomes worn the axis of the valve may become skewed to the axis of the guide and cause the valve to bind within the guide thus increasing engine noise and engine wear. Also, the worn guide and stem may cause accelerated wear to the seal, causing higher oil consumption and interfere with engine emissions. While there is a need to lubricate the valve stem, the problem of oil leaking into the combustion chamber via the valve stem/valve guide interface must also be considered. Increased oil leakage results in excessive smoking and/or high oil consumption within the internal combustion engine. A further factor which compounds all the above problems, is that the valve stem operates in a high temperature environment which may cause the oil to carbonize and reduce the effective life of prior art valve stem seals.
Therefore, it is desirable to develop a valve stem seal which is capable of overcoming the above-mentioned disadvantages of previous valve stem seals.